Like with fresh foods, freshness is viewed as extremely important to the quality of bread. For this reason, bread factories operate late at night, early in the morning, and on holidays to supply freshly baked bread to food stores and the like. Also, in order to provide bread having favorable freshness, “eat-in bakeries” producing and offering bread on-site are increasing in number. Maintaining freshness is thus a critical concern of those in the business of manufacturing and selling bread. Shortening a kneading time of bread dough and early preparation, such as a frozen dough bread-making method, are particularly desired. A frozen dough bread-making method is a method attempting to provide consumers with a freshly baked bread having a favorable taste by freezing bread dough which has already been kneaded, and thawing, fermenting, or baking the bread dough when required. However, yeast in the bread dough is damaged when frozen, and fermentation ability after thawing is reduced. Moreover, gluten formation may be impaired due to glutathione leaking from dead yeast, and the dough may not expand sufficiently when baked into bread.
Modifications to bread-making processes have been investigated in order to improve frozen bread dough quality. The prior art reports a method of completing kneading and fermentation ahead of time, then freezing, and then baking at a place of consumption (Patent Literature 1), a method of freezing without allowing frozen bread dough to ferment, then adding yeast and allowing the dough to ferment after thawing, then baking the dough (Patent Literature 2), a method of adding a quality improver to frozen dough (Patent Literature 3), or the like. In addition, there has been development of, for example, freezing-resistant yeast possessing characteristics in which fermentation ability after thawing is not reduced even when the dough has been fermented ahead of time and then frozen (Non-patent Literature 1 and the like).
However, each of these methods is complex, difficult work, and may not be fully effective in frozen bread dough, for example. Moreover, in recent years, interest in healthiness and in naturalness has increased and there is a trend in which use of chemical and synthetic additives has been severely curtailed.
Meanwhile, yeast contains components such as nucleic acid, amino acid, and peptides. Yeast extract can be used as a source of glutathione, or as yeast extract (a natural seasoning). Efficient use of yeast cell body residue, which is produced in large quantities as a byproduct during extraction, has been pursued. Various methods of producing yeast extract are known which use extracting enzymes, mediums, and the like (Patent Literature 4).
Cell body residue which remains after yeast extract and the like is extracted from yeast contains glucan, mannan, mannoprotein, proteins, lipids, and nucleic acids as primary components. A plurality of known publications address methods of treating such yeast cell body residue and methods of making effective use of the same. For example, Patent Literature 5 describes a method of treating waste water by making a yeast extract residue soluble using a specific enzyme. Patent Literature 6 describes a method of producing mannose by causing a yeast extract residue to be assimilated by microorganisms. Patent Literature 7 describes a method of obtaining a medicinal composition by alkali treatment of a yeast extract residue, followed by irrigation thereof. Patent Literature 8 describes a method of obtaining a microorganism culture substrate material by allowing a cell wall lytic enzyme or the like to act on yeast extract residue. Given the situation, a more effective method of using yeast cell body residue is desired.